A SHORT HISTORY OF QUIET CHINESE GENSETS!
First, there was the internal combustion engine.
Then, the muffler was invented.
Then, the portable generator was invented.
Then, the Chinese copied it.
Then, the Professor "repurposed" the cardboard box.
Then, there was the GenTent.
And now, there is the "Sound Shroud" ... and I've got data!
Here's the setup:
DuroPower 3500ES (electric start) with OEM foam-lined metal enclosure panels, modified with
1) LPG conversion
2) Remote start, manual push button start, enclosed control panel
3) 1/4" Hardiebacker panels all 4 sides and top
4) 500 cfm ventilation fan in top
5) Top carpet-lined and hood added to create ventilation exhaust duct
6) Alternator forced cooling duct with 124 cfm fan
7) Alternator exhaust cooling digital thermometer
๐ RV 30A female pigtail
9) Receiver hitch mount
10) Header/muffler/exhaust wrapped with header wrap and exhaust defuser, exhaust re-oriented down rather than out the genset's side
Here's how all that looks:
With the "Sound Shroud":
The "Sound Shroud" evolved from the Professor's video of how effective a simple cardboard box is for sound reduction. I stumbled across a poly washing machine pan in my garage that had a broken corner. It just struck me that it might make a good starting point for a folding "box" for the genset. I remembered I had another pan over at the old farmhouse sitting under a defunct washing machine. I cut a couple of inches off of one end of one pan so it would nest inside the other (and to get rid of the broken end) and hinged them together with rivets and nylon webbing. I lined the inside of the shorter pan (now the rear wall of the shroud) with carpeting. (3M 77 or 90 spray adhesive will bond to poly plastic - 90's best) I laminated two 4mm thick 24" x 26" sheets of Coroplast (corrugated plastic - a 4' x8' sheet was $20) for each sidewall. (If you orient the two sheets so the corrugations are at right angles, you'll get a stronger, warp-free panel) I bound the edges of the panels with Gorrila tape for durability, and used Gorrila tape to hinge the side panels off of the back poly panel. (If you prime the poly plastic with spray adhesive and let it get tacky, the Gorrila tape will stick tightly) The top outer ends of the side panels are velcro'd to the lid to hold them in place. Not shown in the picture is a short piece of PVC that will be tie-wrapped to the bottom of the genset's frame to support the front lower side panels - I'll probably use Velcro to hold that in place, too.
The whole thing folds flat to about 2 1/2" thick and is fairly light weight.(See the teaser photo a few posts back!);)
Here's the real-world data (genset mounted on back of FW and parked on grass like at AirVenture where I have to boondock) made with a Radio Shack dB Meter with A weighting and fast response on a 4' tripod at 7 meters. "Loaded" is with 15K BTU A/C running, "Left, right, and center" are from the perspective of standing behind the FW facing the genset:
Left: No shroud, unloaded 66, loaded 66
Shrouded, unloaded 62, loaded 63
Right: No shroud, unloaded 64, loaded 65
Shrouded, unloaded 61, loaded 63
Center: No shroud, unloaded 64, loaded 66
Shrouded, unloaded 65, loaded 67
I got some nice reductions left and right (if the meter flickered back and forth, I chose the higher number to report)- the right side is probably more important since that's the side the awning, grill, etc., are on and if you are outside the FW where you are likely to be.
It was curious that the center readings were slightly higher. Of course that's the open location (no panel) on the shroud. Perhaps it is "focusing the sound"? Also, a slight breeze picked up during this measuring, so perhaps that altered things. I also wonder if further reduction would result from lining the roof/lid of the shroud, and also if it might be beneficial to make additional panels that would fold down from the side panels to get the sides closer to the ground?
Inside the 30' FW, seated at the dinette about midway in the super slide (slide open and two chairs in back of FW), the db reading with no A/C running was 51 - shroud or no shroud. With the A/C running and the fan on "HI", it was 56 with the shroud and 57 without.
I realize that I was measuring the A/C's noise as well as the genset's - I could have used a silent load like a heater. However, like I said, this is a "real world" test in that these sounds are what you'll normally hear (most of the time that I'll use the genset will be to run the A/C). I might repeat the tests later with a silent load just for kicks. I'll tweak this later - probably add sound absorptive lining to the shroud's lid and consider the fold-down side panels. It was a fairly inexpensive project - I had all the materials on-hand except for the Coroplast (I like it because it is fairly rigid but extremely light and has the dead air spaces). I think those poly pans are about $15-$20 each, but I happened to have those already. If I hadn't I might have used waterproof hardboard from Lowe's at about $12/sheet.
Regards,
John
First, there was the internal combustion engine.
Then, the muffler was invented.
Then, the portable generator was invented.
Then, the Chinese copied it.
Then, the Professor "repurposed" the cardboard box.
Then, there was the GenTent.
And now, there is the "Sound Shroud" ... and I've got data!
Here's the setup:
DuroPower 3500ES (electric start) with OEM foam-lined metal enclosure panels, modified with
1) LPG conversion
2) Remote start, manual push button start, enclosed control panel
3) 1/4" Hardiebacker panels all 4 sides and top
4) 500 cfm ventilation fan in top
5) Top carpet-lined and hood added to create ventilation exhaust duct
6) Alternator forced cooling duct with 124 cfm fan
7) Alternator exhaust cooling digital thermometer
๐ RV 30A female pigtail
9) Receiver hitch mount
10) Header/muffler/exhaust wrapped with header wrap and exhaust defuser, exhaust re-oriented down rather than out the genset's side
Here's how all that looks:
With the "Sound Shroud":
The "Sound Shroud" evolved from the Professor's video of how effective a simple cardboard box is for sound reduction. I stumbled across a poly washing machine pan in my garage that had a broken corner. It just struck me that it might make a good starting point for a folding "box" for the genset. I remembered I had another pan over at the old farmhouse sitting under a defunct washing machine. I cut a couple of inches off of one end of one pan so it would nest inside the other (and to get rid of the broken end) and hinged them together with rivets and nylon webbing. I lined the inside of the shorter pan (now the rear wall of the shroud) with carpeting. (3M 77 or 90 spray adhesive will bond to poly plastic - 90's best) I laminated two 4mm thick 24" x 26" sheets of Coroplast (corrugated plastic - a 4' x8' sheet was $20) for each sidewall. (If you orient the two sheets so the corrugations are at right angles, you'll get a stronger, warp-free panel) I bound the edges of the panels with Gorrila tape for durability, and used Gorrila tape to hinge the side panels off of the back poly panel. (If you prime the poly plastic with spray adhesive and let it get tacky, the Gorrila tape will stick tightly) The top outer ends of the side panels are velcro'd to the lid to hold them in place. Not shown in the picture is a short piece of PVC that will be tie-wrapped to the bottom of the genset's frame to support the front lower side panels - I'll probably use Velcro to hold that in place, too.
The whole thing folds flat to about 2 1/2" thick and is fairly light weight.(See the teaser photo a few posts back!);)
Here's the real-world data (genset mounted on back of FW and parked on grass like at AirVenture where I have to boondock) made with a Radio Shack dB Meter with A weighting and fast response on a 4' tripod at 7 meters. "Loaded" is with 15K BTU A/C running, "Left, right, and center" are from the perspective of standing behind the FW facing the genset:
Left: No shroud, unloaded 66, loaded 66
Shrouded, unloaded 62, loaded 63
Right: No shroud, unloaded 64, loaded 65
Shrouded, unloaded 61, loaded 63
Center: No shroud, unloaded 64, loaded 66
Shrouded, unloaded 65, loaded 67
I got some nice reductions left and right (if the meter flickered back and forth, I chose the higher number to report)- the right side is probably more important since that's the side the awning, grill, etc., are on and if you are outside the FW where you are likely to be.
It was curious that the center readings were slightly higher. Of course that's the open location (no panel) on the shroud. Perhaps it is "focusing the sound"? Also, a slight breeze picked up during this measuring, so perhaps that altered things. I also wonder if further reduction would result from lining the roof/lid of the shroud, and also if it might be beneficial to make additional panels that would fold down from the side panels to get the sides closer to the ground?
Inside the 30' FW, seated at the dinette about midway in the super slide (slide open and two chairs in back of FW), the db reading with no A/C running was 51 - shroud or no shroud. With the A/C running and the fan on "HI", it was 56 with the shroud and 57 without.
I realize that I was measuring the A/C's noise as well as the genset's - I could have used a silent load like a heater. However, like I said, this is a "real world" test in that these sounds are what you'll normally hear (most of the time that I'll use the genset will be to run the A/C). I might repeat the tests later with a silent load just for kicks. I'll tweak this later - probably add sound absorptive lining to the shroud's lid and consider the fold-down side panels. It was a fairly inexpensive project - I had all the materials on-hand except for the Coroplast (I like it because it is fairly rigid but extremely light and has the dead air spaces). I think those poly pans are about $15-$20 each, but I happened to have those already. If I hadn't I might have used waterproof hardboard from Lowe's at about $12/sheet.
Regards,
John
